Treating iron baths



Dec. 19, 1933. H. BANSEN EHL ,94o,34

TREATING IRON BATHS Filed Aug. 2, 1929 2 Sheets-Sheet- 1 F' 1. WWW/%WWWWWWW n 2. F'g. 3.

Dec. 19, 1933. BANSEN El' AL 9 3 TREATING IRON BATHS Filed Aug. 2,' 19292 shans-Sheet 2 COLD AIR O W vvA s'ra GAS Es i PREHEHTER PREHEATED AIR .Patented nec. 19, 1933 Ari-:Nr OFFICE' 1.9,341 TRATING IRON BATHS HugoBase, Rleinhausen-'n-iemersleim, and- Karl Lbbecke, Rheihausen,Germany', assignors to Fried. K-pp Aktien'gesellsclaft,

Friedrich-Alfred-Hutte, Rleinhausen, .Ger-` many Application August 2,1929, Serial No. 383.069,

and in Germany August 14, 1928 8 Claims.

The invention relates to a process for treating iron baths in steelproducing furnaces;

As' well known, the process of fining the material by the action of "anoxidizing flame upon j the surface of the bath and through theintermediary of the slag cover takes place very slowly when the bath isat rest. Furthermore the heat transmission is very slow. In order toaccelerate these processes a mechanical movement of the o bath bystirrng, rocking or circulating -has been employed and, further, anincreased contact with oxygen is caused by blowing-in air or supplyingore.

The ore causes a motion of the bath only dur- 16 ingthe decarburization.Since it is fed intermittently and in irregular size, an utilization ofthe irregularly developed carbon monoxide by after-combustion isimpossible'. Furthermore, the government of the charge becomes uncertainin 20 fining by means of ores.

According to the invention water is injected into the bath itself whichmeasure aifords several advantages. If the water is injected withsuflicient speed, the injection tube is protected. Furthermore, a highlyvalued oxygen bearer is thus introduced into the bath and, finally, acontinuous movement of the bath is caused by the constant violentdevelopment of hydrogen gas.

By splitting off the oxygen in this fining operation by water less heatis consumed for 1 kg. of

oxygen than in fining by ore.. Furthermore, this quantity of heat may befully converted to useful heat by combustion above the bath and moreparticularly a great useful heat drop can be produced !5 by preheatingthe combustion air up to 1200 degrees by the waste heat, the hydrogenbeing preheated to an average temperature of 1450 degrees C., so that agreat portion of the heat is recovered for the process. Finally, theregular supply and [0 uniform distribution of the water makes possibleThe bath may have any depth and any desired 'portion of a bath can bebrought to seethe so that the process can be employed also' in theopenhearth fmace when'the charge will not start 5 seething. Furthermore.in applying the proc ss to the Thomas or Bessemer process the charge canbe treated as long as desired by heating the bath by theafter-combustion of the gases developed and correspondingly regulatingthe quantity of combustion air. In this manner a notably higher workingtemperature is obtained than for instance by the after-combustion of thecarbon monoxide in a converting process, owing to the dilutionof i thegas by the nitrogen of the fining air being dispensed with. I

The combustion airgis to be conducted so as to come to eflicaciouscontact with the gas that escapes from the entire surface of the bath.The water may be fed by the above-mentioned tube in a. full jet or thetube may be a double walled structure through the outer jacket ofwhichthe water `is fed, in'order to obtain suitable muzzle velocities.

A particular advantage resides in the voluntary supply of the water bothas to quantity and time so that the course of the fining action and ofthe after-combustion can be exactly regulated and the progress of thecharge carefully observed according to the development of the gas.

Any want of heat can be compensated for by addition of fuel. so' Incarrying out the described process simple iron tubes have been found tobe` of short life only so that the process might be rendered un-'economical due to the high consumption -of these tubes. This short lifeof simple iron tubes is due to the prevailing conditions of heattransition and heat conduction. For, the heat transition from theagitated bath to the tube is about equal to that of water to the tubewall, that is amounts about to 2000 to 3000 thermal um'ts, and will benear the upper limit, that is 3000, due to the violent motion of thebath and to the volume of the tube being far smaller than thatof thebath which thus does not undergo any drop oftemperature. If it would bepossible in practice to expose the' entire length of the tube to boilingwater, which would give a heat transition of 4000 to -6000 thermalunits, then a long life of the tube would be Secured, because in thiscase the heat conductivity of iron would have an insulating eifect owingto the-high heat transition prevailing on both sides. Now as the presentprocess provides only the application of a comparatively small quantityof water, this method is not feasible. Hence, the heat transition on thewater side is at best equal to that on the side of the iron bath andconsequently, the tube will be heated up to the mean of the bath andwater temperature or more highly. Therewiththe temperature the tube isexposed to arrives in the 110 I range where the properties of strengthof iron become nearly zero, so that the tube is no' longer capab'le ofresisting the water pressure and mechanical stress and soon will burst.its portions no longer cooled melting off. 4 v

This drawback can be eliminated by the following four measures.

' of the tube so that the time-till its destruction 'may consist inapplying makes possible a' practically and economically satisfactory'execution of the process.

d. By introducing water without a tube.

In the accompanyng drawings are iliustrated several embodiments of themeans for carryi out the described process, in which drawings Figure lshows a 'water-injecting tube in longiv tudinal section,

Figure 2 is acorresponding cross section, v

Figure 3 is' a cross section through a modified water tube,

Figure 4 isa similar section through another modified tube, v

Figure 5 is the elevation of a third modified tube, and

Figure 6 shows an appliance adapted to carry out the process by means ofa movable tube.

A protection of the water tube by reducing or rendering more difficultthe heat transition from the bath to the tube, as mentioned above undera can be obtained in various ways attention being paid to the prevailingspecial conditions, that is to the expansion of the tube and theviolent; mechanical stress and blows to which.

the tube is exposed. So for instance a simple insulation by means oftube-shaped fire bricks has proved unsatisfactory. A good protection,however, is obtained by using a hot stickinz thickly liquid slag, whichslag coating has to be protected. against solidifying and chipping offby preventing it from cooling during the whole operation. To this endthe slag coating preferably is applied to the tube as a liquid slagimmediately before introducing the tube, and is completed from time totime by raising the tube during the' operation so 'that new slag willstick thereto from the slag cover ofthe bath; If this protectivecoating, which in part consists of the content of the bath' itself,possesses the right thickness, a state of balance is obtained betweenthe heat supplied and the heat led oil', whereby the water supply isSecured. Another method to the tube a suitable insulating mass e. g. bymeans of a spraying gun, or by other means.

Now,- as the tube may be heated up to a comparatively high temperaturein spite of the described protection whereby its strength may beconsiderably reduced, itwill be of advantage to provide means forprotecting the tube from bending down. This may be done by fltting thetube with a reinforcing member on the endangered portion such as anU-iron, L-iron or flat iron, as illustrated in Figures 1 to 41:, wherean iron bar a, b or c of suitable section is provided within the tube.As such an iron bar perma- .other hand no danger exists nently remainsat the temperature of the water supplied that is below degrees, itsstrensth is maintained. Care must be taken, however, that the iron barrests on the tube wall only on a few points so that no accumulation ofheat and an increased stress of the tube can take place.

An older method of supplying gaseous, vaporous and liquid substancesconsisted in blowing them in through nozzles provided in 'a wall'of thecontainer, because when the temperature of the bath amounts toconsiderably more than 1000 degrees, a simple s'upply through metallicor refractory tubes is impossible in the course of time. This supplythrough nozzles, however, requires a troublesome tilting or rolling ofthe entire container and, moreover, the quantity supplied can be variedonly within narrow limits. Finally, the supply of a .fining meansrequires special containers or furnaces fltted with the above supplyingnozzles.

In contradistinction thereto thepresent method enables these substancesto be supplied to a melting bath of high temperature by means' of simpletubes'without the container needing be adapted thereto in any way.

The invention resides on the following perception: v

In spite of the considerably higher heat transition from a bath to thetube than from the agent passing through the tube, a certain timeelapses until the tube is heated to its critical temperaure.Furthermore, the destruction of the tube by melting or burning begins atthe place of deepest immersion that is at its muzzle, as here thecooling action upon the tube wall is the feeblest due to the suppliedagent on this place already being at higher temperature. On the for thetube when to a certain slight extent, in which case the agent in thetube is not heated to any considerable extent. The present methodtherefore provides an interruption of this heating and recooling of thetube always shortly before the said critical temperature is reached.This is obtained by so far retiring the tube from the bath while theliquid agent .continues to be supplied, that 'a de-accumulationv of the'heat of the tube wall takes place and the agent which then has itsoriginal low temperature emcaciously cools also the muzzle of the tube.When for 12: instance the agent is supplied in liquid state, theconditions of heat transltion in the bath itself are approximately equalon both sides, but above the bath the transition of heat within the tubeis 20 to 100 times greater than outside. Hence, a violent cooling of thetube wall takes place very quickly.

In .order to protect the tube from destruction, it has therefore to beraised and lowered periodically, the maximum amount of immersion beingdetermined according to the stream velocity .of the agent, thedimensions of the tube, the frequency of the perlod's, and thetemperature of the bath. i

In raising the tube always portions of the bath 14 will adhere to thetube the heat of which portions will be led off so that the attack ofthe bath heat first strikes this protective layer whereby a furtherprotection of the tube is obtained. To attain an emcacious protection of14 this kind that is by a portion of the bath itself, it has provedadvantageous to flrmly wind asbestos cord around the tube on the portionto be dipped before using it, in order to cause the insulatmg bath layermore easily to stick.

dipped only error instance the supp y of the iquid agent an ordinarymelting Iurnace. the depth oi of hioh permits a dipping stroke ot cm..is established by means of ta" is wound on these tubes tor a length 'of1 m., this winding being doubled near the muazie for alength of 15 em.with a supply ot liquid ot aslitersperminutaastrokeoisotoio cin., and adpping trequency of to per minute'the tubes withstand destruction, astests ve proved. ;In

6 one form o; apparat's !or practicing method is illustrated.

the vessel containing the metal bath w the tube ,f is dipped' which isproo' -its length to be dipped with the insu- ,suchasasbestosorthelike.Precombustion air isadmitted intothe space the bath in the vesselthrough p rta p channel q surrounding the top o! the The preheated airis supplied to the q through an inlet pipe h leading from preheater Ic.The eon'bustion gases pass oi! the vessel through a flue i leadingthrough preheater Ic, where their beat is imparted to cold air suppliedto the preheater. In order allowthetubettoberai'sedandlowered epreventing the exit oi!` waste gases aroundtheopeningsinthetopotthevessel In mg. s there is shown, by way ofexample, a hydraulic deviee comprising a cylinder 13 and pisten 14connected by rod 15 with the tube f. A pressure fluid is admitted to thecylinder below which periodically admits the pressure iluid !rom pipe''through port 19 to s e s and alternately tained by increasing the heatabmrbing capacity of the tube by introducing the water into the bath bymeans o! scrap in the form of billet pieces asusuallysuppliedtothebath.Tothisend these 'pieces are provided with a suitable bore.

Furthermo-e, an emcacious protection oi' theasoresorlime,andsupneoessaryiiningwater.

following asatisi'yingresutmoreparticuo! limited' depth. Iu orderapowertul'deeompositionof hydrogenandoxygenthemuazle!Igureksodesignedthatthe Asbestoseordotmmindiameter.-

'arises in the tube causing a premature destruction. To this endthe'contraction coemcient to so be applied has to be so determined thatthe passage area o! the tube is not narrowed.

Finally a reduction ot the dipping depth oi' the tube due to burning ormelting oi! can be lessened by giving the tube a coiied shape, as alsoshown in Figure 5, whereby further a desirable more violent agitation oithe bath is obtained due to the water leaving the tube tangentially.

What we claim and desire to secure by Letters Patent is:- I

1. Process of treating an iron bath to convert it into steel, whichcomprises introducing water inliquid stateinto the bathinsuchamanner asto cause decompositon thereot, and burning the combustible gases ofdec'omposition by supplying combustion air immediately' above thesurface o! the bath.

'2. Process of treating an iron bath to convert it into steel, whichcomprises introducing water 3. Proeess o! treating an' bath to convertit. into steel. which oomprises introducing waterinliquidstateintothebathin suchamanner as to causedecomposition-thereot, and burning the combustible gases ofdeeomposition by supplying combustion air immediately above the surfaceo! the bath, and preheating the combustion air by the waste heat of theprocess.

4. Process of treating an iron bath to convert it into steel, whichcomprises coating an ordinary iron tube with a hot liquid slag,introducing one end oi'-said tube into the bathabeiore the slag cools,and feeding water in liquid form through said tube into the iron bath.:

5.`Process of treating an iron bath to convert it into steel, whichcomprises coating an ordinary m iron tube with a hot liquid slag,introducing one end of said tube into the' bath before the slag cools,ieeding water in liquid form through said tubeintothebath,maintainingacoveringoi slagon the bath, and intermittently renewing the slagcoating* on said-tube by withdrawing the tube i'rom the bathinto thecovesing of slag.

6. Process of treating an iron bath to eonvert it into steel, whichcomprises spraying a hot liquid slag coating onto 'an ordinary irontube, introducing one end of said tube into the bath before said'coatingcools and ieeding water in liquid !om thro said tube into the bath.

'1. Process of treating an iron bath to convert it into steel, which'comprises injecting liquid water into the bath'through a tube insertedinto the bath, periodically partially -withdrawing the tube from thebath while maintaining the flow of water through the tube," andre-inserting the tube to the tull depth atter it has cooled.

8. Process o! treating an iron bath toeonvert it into steel, whichcomprises winding a cord ot retractory material around an ordinary irontube,

'dippingoneendotsaidtubeintothebatm teed ing water in liquid formthrougipsaid tube into the bath. and periodically raising the tube tocause substaneesfrom thebathtoadhere thereto.

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